1. Field of the Invention
This invention relates to an improvement in coating compositions containing polyarylene sulfide resin. The improvement is the addition of a modifying compound which contains a monovalent alkali metal to the coating composition. Coatings produced by the improved coating composition can be lighter in color, if desired, than those produced by known polyarylene sulfide resin coating compositions.
2. Prior Art
Cookware which is non-stick because it is coated with resins of various sorts has come into widespread use in recent years. People prefer to use non-stick coated cookware because food is less likely to stick to it than to uncoated cookware, and because it is so easy to clean.
For coated cookware to have broad customer appeal, it should be available in a broad spectrum of colors ranging from the lightest to the darkest. Unfortunately, not all resins useful to produce non-stick coatings are available in such a broad spectrum. Polyarylene sulfide resin is one which is not; when polyarylene sulfide resin is baked and coalesced to produce a coating, it discolors to a dark tan color. To help overcome this discoloration, pigment, such as titanium dioxide, is mixed with the resin; however, this mixture produces a coating which, at best, is a light tan.
British Pat. No. 1,358,428, published July 3, 1974, discloses compositions containing flurocarbon polymers, polyphenylene sulfide, lithium hydroxide and cobalt octoate along with a pigment and a dispersing agent. The lithium hydroxide is used in crystallized from and is thought to improve the adhesion of the coating to the substrate. Pigments or carbon black are included in the examples of that British patent, and it does not teach a method of lightening the color of resultant coatings. Also, lithium hydroxide has been found to be inferior to compounds of other alkali metals in lightening the color of polyphenylene sulfide coatings.